Ice on Land Flashcards
(55 cards)
1
Q
What does the trem ‘Ice Age’ mean?
A
A period of time when ice sheets are found
on continents. We still have glaciers on land
today, so strictly speaking we are still in an
Ice Age.
2
Q
How long has the recent Ice Age
lasted?
A
Scientists believe that the climate has been
similar for the last 2 millions years or so.
3
Q
What is the recent Ice Age called?
A
Pleistocene Era
4
Q
What has happened within these 2 millions years of the Pleistocene Era?
A
During that time, the glaciers have advanced and retreated and in doing so has created many impressive landscapes. In fact, Britain would have looked like Greenland in the past.
5
Q
What the names given for the periods for when
glaciers advance and retreat?
A
Warmer periods are called inter-glacial periods and colder periods are called glacial periods.
6
Q
During the most extreme glacial periods during the Pleistocene what happens ?
A
Britain was almost completely covered by a huge ice sheet
7
Q
How do we know the climate has done this ? (3 ways)
A
- Glacial land-forms
- Fossil evidence of animals/plant
- Ice core evidence
8
Q
How do we know the climate has done this : Glacial land-forms
A
These are found in places like Scotland and the Lake District = ice must have been there (glacial period).
9
Q
How do we know the climate has done this : Fossil evidence of animals/plant
A
When found in warmer climates proves that there have been warmer periods (inter-glacial period). For example, dig down in Trafalgar Square in London and you found skeletons of Rhino and Lion. These sediments are dated at just 100,000 years before present (BP).
10
Q
How do we know the climate has done this : Ice core evidence
A
At the start they were drilling for ice cores. Each year, a new layer of ice is created (a bit like the rings on a
tree), which means that you can drill down and look back in time. Crucially, air bubbles are trapped in the ice and if you can get to them you can analyse the chemical composition and infer what the climate was like.
11
Q
How is a glacier created?
A
- When snow accumulates, the weight of the snow compresses the air out of the snow below and this causes snow to turn into a firn
- After about 20 years this air is completely eradicated and the firn turns into a glacial ice
- When you compact the snow together it becomes denser and becomes more ice-like. Ice that is resting on slopes will move due to gravity
- when the ice begins to move it is called a glacier.
12
Q
What are the different types of glacier?
A
- A valley glacier is like a river of ice. It flows from high areas and follows the easiest route down – often in preexisting river valleys
- An ice sheet is a huge mass of ice that covers a vast area - e.g. Greenland or Antarctica. These account for 96% of ice on Earth
13
Q
Glaciers move: how does this happen?
A
- Glaciers move due to gravity
- However the rate of movement is due to the GLACIAL
BUDGET - This is the difference between the accumulation and ablation of ice each year.
- Glaciers have an accumulation (adding more) zone at the top, where it is coldest.
- However, as the glacier moves downhill the temperature increases and the ice will
melt. This is called ablation (melting). - The balance of the accumulation and the ablation will determine whether a glacier moves forward (advance) or move backwards (retreat) – i.e. as suggested by
the glacial budget.
14
Q
What example should you use for a glacier that is
changing?
A
- The Mer de Glace (Sea of Ice) in the French Alps- the largest glacier in France; 7km long and 200 metres deep.
- It flows from Mont Blanc towards Chamonix.
- It has been getting shorter and thinner since 1850
- Advance in the 1970s and 1980s by about 150 metres has given way to retreat
- It is retreating by about 30 metres a year (500 metres
shorter than in 1994).
15
Q
Evidence that Mer de Glace is retreating :
A
- Photographic evidence, but also through 19th Century paintings. Aerial imagery, old maps and debris left by the glacier all provide evidence of previous positions
- The Mer de Glace is retreating due to climate change. - Temperatures are 1⁰C higher than 100 years ago, and 3⁰C higher above 1,800 metres
- Combined with drier winters (i.e. less snowfall) the glaciers are melting away.
16
Q
What about other changes to glaciers?
A
- Glaciers change on a seasonal basis too; they tend to
advance in the winter and retreat in the summer. - Therefore, when trying to assess whether a glacier is
in a state of advance or retreat, you really should
compare position from Winter to Winter or Summer
to Summer
17
Q
How does a glacier shape the land?
A
There are three main erosion processes; Bulldozing,
Abrasion and Plucking.
18
Q
Plucking :
A
When a glacier moves over an area of rock. Due to friction, the glacier melts and water seeps into crack around the rocks below. The water refreezes and the rock effectively becomes part of the glacier and is ripped out when the glacier continues to move forward.
19
Q
Abrasion :
A
When rocks at the bottom of the glacier act like sandpaper – grinding over the bedrock. This can polish the rocks or create sharp grooves called striations.
20
Q
Bulldozing :
A
When rocks that are in front of the glacier are physically removed by the advancing glacier.
21
Q
Where does weathering fit into this?
A
Weathering is the break down of rock in situ (i.e. no movement) by the process of the weather
The glaciers do not have anything to do with this process!
However, the rocks that are shattered from the rock faces in this way can then be used for abrasion or bulldozed away by the glacier
22
Q
Landform created by erosion : Corries (called Cirques in France and Cwms in Wales)
A
- Often found in North facing slopes. Snow doesn’t melt in the summer and a glacier forms.
- Plucking and freeze-thaw weathering remove rocks from the backwall making them very steep.
- Abrasion occurs at the base when the glacier starts to move (rotational slip due to the weight) – rocks fed by freeze-thaw weathering helps this (Bergschrund crevasse allows rocks to fall through the glacier).
- Less erosion takes place at the front of the corrie (less weight), so a rock lip is formed (moraine can also build up here).
- When the ice has gone this feature acts as a dam for a tarn to form.
23
Q
Landform created by erosion : Arête
A
- An arête is a sharp ridge cut when two corries either side of a mountain cut back to back
- The back/ side wall of each corries is attacked by freeze-thaw weathering and plucking leaving a sharp ridge between them.
- The picture on the left is Striding Edge in the Lake District.
24
Q
Landform created by erosion : Pyramidal Peak
A
- When you have three or more corries surrounding a mountainside, they cut back and produce this feature
1) Glacier forms in hollows
2) Backwalls worn away
3) Ridge is narrowed
4) Arête is formed
5) Pyramidal peak develops
25
Landform created by erosion : Glacial Trough
- Due to abrasion, plucking and bulldozing, the glacier will erode the landscape as it moves downhill
- Glaciers tend to occupy a former river valley and the erosion turns the V=shaped cross section into a U-shaped one
26
Landform created by erosion : Truncated Spurs
- River valleys have ‘Interlocking spurs’ like the teeth in a zip that overlap
- However, a glacier removes them and makes the valley straight
27
Landform created by erosion : Hanging Valleys
- The main glacier is the most powerful at eroding the landscape and cuts down quicker than the smaller valley glaciers that feed into it
- Therefore, once the ice has melted away, you are left with a main trough with small troughs feeding into the main valley
- However, the smaller troughs are way above the main valley as a result of their weaker erosive force.
- Waterfalls are often found cascading from the hanging valley into the main valley
28
Landform created by erosion : Ribbon Lake
- Ribbon Lakes are formed when a glacier moves down a valley and moves over an area of softer rock
- This rock is eroded (abrasion/plucking) far more easily than the surrounded rock and the valley is over deepened at this point
- When the glacier retreats the hollow left becomes filled with water and a ribbon lake is formed
- These are long and narrow and occupy the U-shaped valleys – e.g. Lake Windermere in the Lake District.
- Ribbon lakes can also be formed by deposition too.
- When a terminal/ recessional moraine is left by a glacier, this can act like a dam and trap the water behind to form a lake.
29
How do Glaciers transport material?
Freeze-thaw supplies rock that fall onto the glacier.
| Glaciers can also bulldoze rocks in front of it.
30
Why does a glacier deposit material?
- When a glacier melts it can lose energy. Any material that is carried can therefore become deposited.
- Material that is carried/ deposited by a glacier is called moraine
- Depending on the amount of weathering/ erosion that
has taken place on the material this will determine its size
- Small, fine sediment is called rock flour
-Slightly larger sediment is called boulder clay or til
- Large boulders dumped away from their source are called erratics.
31
What depositional landforms are created by glaciers : Moraines
- Moraines are left by a glacier.
- Ground moraine is the layer left under the glacier
- Lateral moraine is found along both edges of the glacier; it is the weathered rock that has fallen
from the valley sides. When these melt, ridges are left at the side of the valley.
- Medial moraine is where two glaciers have joined together to form a larger glacier
- The lateral moraine of the two glaciers will be in the middle as a result.
- When the glacier melts a ridge will be found along the middle of the valley
- Terminal moraine is dropped at the end of the
glacier at its snout. This can be used to show the maximum extent that the glacier reached.
32
What depositional landforms are created by glaciers : Drumlins
- Drumlins are formed when glaciers shape the
moraine on the valley floor into small hills
- They have a blunt end and a tapered end
- They are found in swarms and the landscape is described as having a ‘basket of eggs topography’ (e.g. Hellifield in the Yorkshire Dales ).
33
What case study can be used for Winter Sports in Glacial regions?
- La Plagne
- 120 million visitors go to the Alps each year for winter sports such as bobsleigh, skiing, snowboarding, rock/ice climbing etc
- La Plagne has tapped into this market.
34
La Plagne : When
Built in 1960s
35
La Plagne : Where
French Alps, 2000 metres up
36
La Plagne : Why
- Economical benefits
- Good location as the height guarantees snow from December to
April (i.e. long season) and a glacier (Bellecote) which can guarantee skiing, even in the summer.
37
La Plagne : What other positives does La Plagne possess?
- Large selection of bars, restaurant and nightclubs
- Variety of slopes for all abilities
- Ski to doorstep
- Not just skiing – other winter sports available
38
La Plagne : Recent developments:
- Great access (train, 4 airports nearby and access to motorway network) made it very popular
- It now has six villages all interlinked by a quality lift system
- It has even been linked up to Les Arcs to produce a huge ski area
- Expansion was done ‘in-keeping’ with the environment: buildings built in a traditional style, rather than just building ugly tower blocks.
39
What case study for all year round tourism?
Mer de Glace, Chamonix
40
Chamonix :
- It has Europe’s highest mountain – Mont Blanc
- It has a permanent population of 10,000, but this can swell to 100,000 in winter (snow sports) and 130,000 in summer.
- The reason people go in the summer is the beautiful countryside, hiking, walking, mountain biking, shops, restaurants and the Mer de Glace
- The Montenvers train takes people to the edge of the
glacier. It was built in 1908
- Once at the glacier, tourists can experience the ‘Ice Cave’ which has been carved in the glacier.
41
Chamonix :
- It has Europe’s highest mountain – Mont Blanc
- It has a permanent population of 10,000, but this can swell to 100,000 in winter (snow sports) and 130,000 in summer.
- The reason people go in the summer is the beautiful countryside, hiking, walking, mountain biking, shops, restaurants and the Mer de Glace
- The Montenvers train takes people to the edge of the
glacier. It was built in 1908
- Once at the glacier, tourists can experience the ‘Ice Cave’ which has been carved in the glacier.
42
What are the issues related to tourism in the Alps : Economic
- Thriving economy as a result of tourist spending
| - Tourism is allyear round. Demand for services is maintained throughout the year, creating jobs
43
What are the issues related to tourism in the Alps : Social
- Young people stay when they leave education –
many job opportunities
- way of life changed – decline in local crafts and skills
44
What are the issues related to tourism in the Alps : Environmental
- Large amounts of water needed for the resorts for
drinking/ snow making
- Noise from machinery scares wildlife
- Forest cleared for slopes- soil erosion and water cycle
- Skiing damages vegetation underneath
- An increase in vehicles has led to air pollution – this
is often trapped in the Alpine valleys. This damages
trees
45
How is tourism being managed : La Plagne
- New building built in traditional style (wood)
- Underground parking – ski to hotel and limits
pollution in the resort
- Some of the villages are above the tree line, so
tree cutting not an issue
- Avalanche fences built for protection
- Part of the Vanoise National Park- conservation a
key focus
46
How is tourism being managed : Chamonix
- The council has developed a policy of ‘integrated
tourism’, which educates and involves visitors and local
people in the protection of the Alpine environment. It: - Free public transport (reduce car usage)
- Encourage local farming
- Education about the Mer de Glace
47
What are Avalanches?
An avalanche is a rapid flow of snow down a slope. It can be a natural event of caused by human activities.
48
How are avalanches created?
- Heavy snowfall
- Rise in temperature – weakens the upper layers of snow
- Wind direction – can build up snow on one side of the mountain. This overhangs on
one side and can become loose
- Slope angle. Most avalanches occur on slopes between 30⁰ and 50⁰.
- Type of slope – convex slopes are more prone to avalanches than concave slopes
49
How are avalanches created : humans
- Off-piste skiing disturbs the slopes, as does walking and climbing
- Removal of tress from slopes prevents the snow from being kept in one place too,
thus increasing the risk of avalanches
50
What are the effects of avalanches?
- Loss of life – people buried and die of hypothermia if not found within minutes.
- Injuries – broken bones and other serious injuries
- Buildings buried/ destroyed
- Roads blocked, which slows rescue efforts
51
What can the longer term effects of an avalanche be?
- Small avalanches often cause little disruption
- However, a major avalanche can cause serious problems
- Fear of a repeat incident can keep the tourists away.
- The lack of facilities (destroyed) can also keep tourists
away
- A loss of tourists can lead to the failure of businesses and therefore loss of jobs can occur.
- The avalanche at Montroc, near Chamonix, killed 12 in 1999 and destroyed 20 houses
52
What is happening to Europe’s glaciers?
- They are retreating
- As has been mentioned previously, temperatures have risen by 1⁰C over the last century and has risen by 3⁰C over 1,800 metres in the last 40 years
- The Mer de Glace is 500 metres shorter than it was in 1994
- Winter snowfall is unreliable and the lower Alps is receiving less total snowfall overall
- These will cause real problems for glaciers.
53
What impact will the retreat of the glaciers have : Economic
- Some resorts will no longer be viable as
Winter resorts- this is a real problem in the
southern Alps. Fewer siightseers and ice
climbers will be a problem in all resorts.
- Less tourism will result in less income for the
area
- However, the big, high-altitude resorts, should
prosper as people are forced to go to them.
- They have the facilities and amenities already
and the ability to make artificial snow.
- Agriculture could benefit from a higher
snowline and warmer summers – a longer
growing season
54
What impact will the retreat of the glaciers have : Social
- Jobs could be lost if tourist numbers fall – higher unemployment
- With no jobs, young people will leave to find work – change in the population structure
- Services could decline, but the elderly that remain will demand more
55
What impact will the retreat of the glaciers have : Environmental
- The Alps is a ‘fragile environment’, which means it is easily damaged
- A delicate balance exists, so the increase
in temperatures/ loss of snow could mean that it is
unihabitable for some species.
- Less water, so river levels will drop that have their source in the Alps.
- More avalanches
- Flooding from melting glaciers
- Rock falls as the ground thaws
